Staircase mold assembly

ABSTRACT

A molding assembly for cement or concrete staircase construction is disclosed. The assembly consists of an elongate support member and a plurality of riser support plates pivotally carried by the elongate support member with each of the riser support plates having a substantially upright edge portion and means to secure a riser board against which concrete is poured to each of the upright edges of the riser support plates. The assembly is also provided with elongate guide means which extend longitudinally of the elongate support member with the riser support plates being pivotally secured to the elongate guide means. With this arrangement longitudinal movement of the elongate guide means imparts uniform rotational movement to each of the riser support plates and results in the upright edges of the riser support plates being substantially vertical regardless of the angle of inclination of the staircase and of the support member. It is usual that the assembly is employed in pairs, but three or more such assemblies could be employed depending upon the width of the staircase.

[111 3,823,910 v[ Julyl6, 1974 [541- STAIRCASE MOLD ASSEMBLY 2 0 3 a um i Z 0 r CE. eS .n 1% r. era vDm a C Lm r0 umfl hr flaw AFA [76] Inventor:

[57] ABSTRACT A molding assembly for cement, or concrete staircase construction is disclosed. The assembly consists of an elongate support member and a plurality of riser suplates pivotally carried by the elongate support of the riser support plates having a pright edge portion and meansto secure a riser board against which concrete is poured to each of the upright edges of the riser support plates. The assembly .is also provided withelongate guide means whichextend longitudinally of the elongate support a member with the riser support lplates being pivotally secured to the elongate guide means. With this arrangement longitudinal movement of the elongate guide means imparts uniform rotational movement to each of the riser support plates and results in the upright edges of the riser support'plates being substantially vertical-regardless of the angle of inclination of' the staircase and of the support member. It is usual that the assembly is employed in pairs, but three or .yed depending .m p m 6 e b M u o ,C S .w h b C m a C e S, h RN M m If. U otmm t 6 m r. New 0 pmS m M4/09 44444 W m HHHHH 2 93 99999 2 7 44444 1 222225 r. "N 1 m m wm m m. m 9 m T m a n S m H m D u N u C u 1, ,u n .l. n W "7 E u L .n n n T m JP m .w m "8 w m L r n .n m Am 2 P n C r" "M a 7 n n u. SS,& mm 9 m m mmmom B 1 HM "n CT a me t a .u .nA lnh g .a 8 1 c a nu" e C Mm e .l m IT uaet N r. t N .RSWFPPS G P m .P m MD T & 2 ,A H m E 8967 A O n 9 .9.9 67 6 O. gJI .8 [0000999 9 N m NHHHHHNH O 2557O 6 0 l .l 11 m N F m s .m E H D. e m 52792 4 F A surr, mmwwm w i y 1 vF l l l 1]] 1 64212 .6 2 l 0 2 8 6 l2m3l 3 2 2 3 555 5 66 13,6, 8 [L 33 249/14 upon'the width of the staircase.

' i 11 Claims, 8 Drawing'Fig ures Primary Examiner-Robert D. Baldwin Assistant Examiner-John McQuade Attorney, Agent, or Firm-Browdy & Neimark PATENTEDJUHBIW I 3.823810 summra PATENTED JUL 1 6 I974 SHEET 2 [IF 3 1 STAIRCASE MOLD ASSEMBLY The present invention relates to a concrete molding or forming structure, and particularly to a mold structure for concrete or cement for use during the construction of staircases.

In the past, forms or molds for receiving concrete for the erection of concrete staircases have consisted of on site erection of the forms by skilled workmen who after providing for the underflooring or decking provide in clined and spaced apart riser assemblies, between which riser assemblies are positioned suitable riser boards to determine the extent of the rise of each step. With this arrangement'it is necessary for the workmen to measure and calculate each riser board positioning to determine that each step has a similar rise and tread depth and this method is both time consuming and wasteful of materials. 1

The present invention overcomes the disadvantages presently encountered in the building and formation of molding forms for the pouring of concrete'by providing a support or stringer assembly, which are usually used in pairs, with each stringer assembly carrying a plurality of risersupport plates, the plates being so interconnected together by a longitudinally extending guide assembly that the positioning of one of the plates results in a corresponding positioning of all of the remaining plates carried by the stringer. Thus with the apparatus of the present invention by positioning one of the riser support'plates in a desired position the remaining riser support plates all assume a corresponding position with the result that the rise of each step and the depth of tread on each step are similar throughout the whole length of the staircase regardless of the angle of inclination of the stringer assembly. I

An object of the invention is to provide a. concrete molding structure which will eliminate loss of building materials and labour time in the laying out and the cutting of wooden stringers and to provide a simple and time saving mold assembly.

A further object is to provide a concrete or cement molding structure which will assist in carrying the weight of various molding forms and concrete and will provide a saving both in bracing and shoring which are normally used to support a molding structure during the pouring of concrete.

These and other objects of the present invention will become apparent fromthe following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view of the positioning ofv the apparatus of the present invention after pouring of a concrete staircase has been completed;

FIG. 2 is an enlarged exploded view of a portion of a support member or stringer arrangement according to FIG. 1;

FIG. 3 is an enlarged sectional viewof one of the support members or stringer arrangements shown in FIG. 1 taken generally along line 3--3 of FIG; '1;

FIG. 4 isan enlarged sideelevation of a portion of a' support member or stringer assembly shown in FIG. 1 with a side member removed to illustrate a further embodiment of the inventive concept;

' FIG. 5 is an enlarged side elevation of a portion of a support member or stringer assembly shown in FIG. 1 with a side member removed to illustrate a still further embodiment of the inventive concept;

FIG. 8 is'a side board as shown in FIGS. 5 and 7 illustrating the positioning of elongate slots therein.

The apparatus shown in FIG. 1 will now be discussed in detail and reference should also be had to attached FIGS. 2 and 3 wherein like reference numberals refer to like component parts.

The inventive apparatus-shown in FIG. 1 consists of two elongate support or'stringer members, each of which is generally indicated by numeral 2. Each of the members 2 consists of two parallel and spaced apart side members 4 and 6 which are held together in parallel and spaced apart relationship by a spacing plate 8 which is secured to the members 4 and 6 by suitable means such as nails or bolts if the members 4 and 6 and plate 8 are made of wood, or by bolts or welding if the members and plates are of 'a metallic material.

Apertures or holes 10 are provided in each of the side members 4 and'6, and bolts or rivets 12 are positioned in the hole and extend through the side members as is well shown in FIGS QZ and 3.

Each of the rivets or bolts 12 form a major pivot pin and a riser support plate 14 having an aperture 16 is pivotally supported on each major pivot pin 12. Spacing washers l8 and 20 are provided on the pivot pins 12 between the plate 14 and the side members 4 and 6 respectively.

- The outer upper corner of each riser support plate 14 isprovided with a comer hole or corner aperture 22'to receive a rivetor bolt 24 which provides a corner pivot pin and which also extends through a'hole 26 provided in a'longit'udinally extending elongate guide means or rod 28.

All of the riser plates 14 are identical in configuration with the exception of the lowerpost plate 14a (the purpose of which will be described in more detail below) and'all of the plates 14 and 14a are provided with the apertures 22 and are pivotally secured to the guide rod 28 by bolts 24 in the manner indicated.

' Each of the riser support plates 14 and 14a are pivotally mounted between the side members 4 and 6 by means of the major pivot pins 12, and eachof the riser support plates '14 and 14a are pivotally secured to the guide rod 28 with the result that longitudinal movement of the guide rod results in an equal and uniform pivoting of each of the plates. Thus, when the support or stringer members 2 are positioned over preassernbled decking prior to the pouring of concrete, it is a simple matter for a workman to' longitudinally move the guide rod 28 to provide the correct rise and treat portion of each step to be formed, and as all of the riser support plates are pivotally interconnected then all of the plates will assume a uniform positioning regardless of the angle of inclination of the ber or steepness of the staircase.

As indicated above, all of the riser support plates 14 remaining plates 14 having a generally truncated tri-' angular configuration (see'FIGS. Sand 7 All of the support mem plates are provided with an inner or riser edge 30 and in the case of the lowermost riser support plate 14a, the riser edge is positioned at 90 or at right-anglesto the lower tread edge 32. Due to the pivoting interconnection of all of the plates the riser edges 30 on all of the plates will be substantially vertical when the lower tread edge 32 of plate 14a is horizontal regardless of the angle of inclination of the support members 2. Thus, by using the present apparatus, a workmans job is considerably simplified inasmuch as it is no longer necessary to measure and calculate the various riser and tread angles and depthand it is only necessary to position the structure and the tread depth and riser height become automatically calculated and it is necessary only for workmen to position and secure suitable riser mold boards to the riser edges on the various plates before commencement of the pouring of the concrete.

In the case of riser support plates 14 the lower edges 32 are provided at an acute angle to riser edges 30 to enable a workman to trowel beneath these riser support plates during smoothing of the cement or concrete forming the tread portion of each step.

In order to position the assembly, each of the members 2 is provided with suitable clamping members 34 to receive rods 36 projecting upwardly from the preassembled wooden decking 40. Other methods of securing the members 2 in place are of course possible but the disclosed arrangement is quite feasible.

The use of the apparatus according to the present invention will now be described with reference to accompanying FIG. 1. I

In constructing a concret e-staircase,a workman first positions supporting timbers 38 and these timbers are then covered by wooden decking 40 in known manner.- In order to confine the width of the staircase, side forms 42 are then positioned, also ina known manner.

' The side form 42'on the right-hand side of the staircase as viewed in FIG. 1 is shown only in broken lines for a better understanding, and also it will be appreciated that the side member 4 of the left-hand stringer member 2 is shown as being partially broken away also for a clarification of the drawings.

After the supporting timbers and wooden decking and side forms are assembled, support'posts 36 are then positioned either by driving them into the wooden decking or by screwing them into the wooden decking if the support posts 36 are provided with screw threads. After the posts 36 are positioned the members 2 are then mounted in position with the clamping devices 34 engaging over the posts 36. If the concrete flooring 43 has already been poured and hardened the edges 32 of the lowermost riser support plate 14a are simply placed on the concrete surface and the riser edges 30 of the remaining plates 14 will assume a vertical positioning regardless of the angle of inclination of the support members 2, as already discussed above.

If concrete 43 has not yet been poured the guideirods 28 are then moved longitudinally within the support assembly until the tread edges 32 of the lowermost riser support plates 14a are in a horizontal position and this positioning of the lower support plates 14a will positively ensure that the riser edges 30 of each of the riser support plates 14 assumes a vertical position and also that the tread depth of each of the individual steps is identical. After the guide rod is positioned it may be held in the selected position by means of a suitable clamping mechanism not shown in the drawings. Such a clamping mechanism may consist however of a sleeve secured to the support member 2 and through which the guide rod 28 passes, and the sleeve may be provided with a set-screw bearing on the rod to hold the rod infposition. When the stringer and riser support plates are suitably positioned it is then only necessary for a workman to position and secure suitable riser molding'boards 44 onto the riser edges of the various riser support plates. It is usual howeverthat the riser mold boards-be secured to the riser support plates prior to the actual positioning of the members 2. The riser edges of each of the riser support plates 14a and 14 may be provided with inwardly 0r outwardly directed flanges (not specifically shown) having holes or apertures provided therein and through which nails or screws may be inserted to maintain the mold boards 44 in position. I I

However a preferred construction for securing the mold boards 44 to the various riser support plates is illustrated in FIGS. 1, 2 and 3. From these drawings it will be appreciated that the riser edge 30 'of each riser support plate 14 and 14a is provided with an adjustable riser board support plate 46 which is pivotally secured to the innermost upper corner of each riser support plateby means of a pin or rivet 48.-The lowermost inner corner of each riser support plate is provided with an aperture 50 to receive a pin or bolt 51 and which is also to be received within any of the three selected apertures 52, 52 and 52" provided on the lower portion of the adjustable riser board support plate 46. The latter plate is also provided with 3 an inwardly (or outwardly) directed flange 54 which is also provided with suitable'apertures 56 by means of which the flange may be securely fastened to molding board 44. In attached FIG. 4, the right-hand riser board support plate 46 is shown having flange 54 secured to moldingboard 44 by means of nails 58 which pass through aperture 56.-

FIG. 4 illustrates the function of the adjustable riser angle support plates 46. In the left-hand support plate 14a shown in FIG. 4, the angle plate 46 is closed tightly against riser edge 30 with pin 51 passing through aperture 52 provided in the angle plate. In this position the riser board will be held in vertical 1 position so that the finished riser surface of the concrete steps will be vertical. The centre riser support plate 14 shown in FIG. 4 illustrates the positioning of the angle plate 46 when it is desired to have the riser portion of a finished step inclined slightly outwardly. When this is desired, the

angle plate 46 is pivoted by means of pin 48 outwardly from the riser support plate and pin 51 is inserted into aperture 52' provided in the angle plate. If further inclination of the riser surface is desired (and this is shown in the righthand riser support plate shown in FIG. v4) the angle plate is pivoted further "outwardly from the riser support plate 14 and pin 51 is inserted into aperture 52 provided in the angle plate. While only three apertures 52, 52 and 52" have been shown in the attached drawing, it will be apparent that any number could be selected to provide a more precise regulation of the actual riser inclination, and moreover other means of; maintaining the riser angle in a secure position with respect to the riser support plate could be utilized without departing from the scope of the present invention. Modifications 0f the basic inventive concept described in the foregoing disclosure and shown in accompanying drawings numbering FIGS. 1 through 4 are p of course possible without departing from the scope of the present invention.

Further embodiments of the present invention are illustrated in attached FIGS. 5 through 8.

In FIG. 1, the major pivot pins 12 are fixed within apertures and no longitudinal movement of the pins is possible with the result that it is not possible to adjust the spacing of the riser support plates with respect to each other along the support or stringer assemblies. The embodiments shown in the attached FIGS. 5, 6, 7 and 8 illustrate modifications wherein such spacing is possible.

With respect to attached FIG. 5 which is a side view of one of the stringer assemblies with the closest side member removed for a better understanding, side member 6' is identical with earlier described side member 6 with the exception that instead of the apertures 10, side member is provided with elongate slots 60 (see broken lines in FIG. 6 and also in FIG. 8) and the major pivot pins 12 are positioned within these slots. The pivot pins 12 support the plates 14a and 14 for both pivotal and longitudinal movement within the slots 60 and longitudinal movement of the pins in the slots is controlled by lazy-tong arrangement consisting of linkage numbers 62 and 64 which in addition to being pivotally secured together by means of pin 60 are also pivotally attached by means of pivot pins 68 and 70. With the arrangement shown in FIG. 5, it will be appreciated that actuation of the lazy-tong arrangement will result in a spacing of the riser support plates 14, longitudinally within the support assemblies'2 and that the plates 14 will always be equally spaced apart. In the embodiment illustrated in FIG. 1, the depth of tread of each step will always be the same and will depend upon the actual angle of inclination or steepness of the staircase, i.e., the steeper the staircase, the narrower the tread depth, and vice versa; whereas using the embodiment illustrated in FIG. 5 a workman may selectively position the riser support plates within the-stringer assemblies to regulate the depth of step tread regardless of the angle or inclination of the stringer assemblies.

To permit such a longitudinal movement of the plates 14 within the stringer assembly, the radius or guide rod 28 is'not attached directly to the riser support plates 14 but rather the riserv support plates are pivoted to sleeve members 72 by means of pin 24. The sleeve members 72 are slideable along the guide rods 28 and after operation of the lazy-tong arrangement to space the plates the desired distance apart set-screws'74 on each of the sleeves 72 are tightened to pivotally secure the guide rods to the various plates. When the set-screws 74 are tightened, longitudinal movement of the guide rod will of course result in a uniform pivoting arrangement of the risersupport plates in a manner described earlier with respect to FIG. 1. All of the pins of the assembly shown in FIG. 5 pass through the slots 60 with the exception of the lowermost pin l2'which passes into an aperture 10 as shownin FIGS. 1 and 2. Thus, major pivot pin 12 which passes through angle support plate 14a is restrained against any longitudinal mo-ement and operation of the lazy-tong arrangement will uniforrnly move the remaining angle support plates 14 with respect to the lowermost support plate 14a which is'stationarily pivotally mounted within aperture 10.

For a better understanding of the structure illustrated in FIG. 5, reference is had to attached FIG. 6 which is a line taken along line 66 of FIG. 5 and which illustrates both side members 4' and 6' in position. A spacing member 20 and suitable washers are of course provided to facilitate the pivoting movement. In FIG. 6 the pivot pin 12 is shown having enlarged heads 76 on each end with the heads being of course bearing washers 78 to prevent displacement of the pins from within the slot stringer or support assembly according to the present invention and is similar to FIG. 5 with the exception that a different arrangement for spacing the riser support plates within thestringer assembly is shown. In FIG. 7, the various riser support plates 14a and 14 are pivoted with respect to guide rod 28 in the manner described above with reference to FIGS. 5 and 6; Also pivot pin 12 passes through the side members 4' and 6 and is received within the lowermost aperture 10 and the slots 60 in a manner also as described above. However, in FIG. 7 the lazytong arrangement of FIGS. 5 and 6, is replaced by a telescoping arrangement generally indicated at 80 in FIG. 7. Over each of the major pivot pins 12 an internally threaded sleeve 82 is provided. An adjustment rod 84 extends between each adjacent sleeve 82 and the rods are externally threaded on each end to be received within the sleeve members. The external threading on each end of the rods 84 is reversed as is the internal threading in the facing ends of each adjacent sleeve 82 with the result that individual rotation. of each of the rods will result in either aclosing together of the riser support plates or an opening apart depending of course upon the direction of rotation of the rod..ln the embodiment shown in FIG. 7 the rotation of each rod must be made individually by hand. After the rods have been rotated and'the various riser support plates correctly positioned, the set-screws 74 are then tightened so that pivotal movement of the various riser support plates are controlled by movement of the guide rod 28.

As a further alternative to the embodiment shown in FIG. 7, the sleeve 72 surrounding the guide rod could be replaced by internally threaded sleeves (not shown) much the same as sleeve 82 and the guide rod itself could be replaced by adjustment rods (not shown) which are externally threaded on each end as in the manner of rods 84 to be received within the internally threaded sleeves. Thus rotation of the rod various adjustment segments will result in longitudinal movement of the riser support plates within the stringer assembly.

Rather than having. the side members 4 and 6 provided with elongate slots such as shown at 60, the side members could be formed by upper and lower members (not shown) having a longitudinal space therebetween to receive the major pivot pins 12. Such upper and lower members would of course be secured together by suitable means. Alternatively each of the side members could be provided with a-longitudinally extending inner groove to receive opposite ends of the pins 12.

Further various modifications of the structure disclosed are of course within the framework of the present inventive concept.

It is usual that the support assemblies be used in pairs as shown in FIG. 1. However, only one such assembly,

or three or more could be used depending upon the width of the staircase.

The materials employed in the construction of the adjustable stringer assembly are of course simply a matter of choice. The various pivot pins are preferably made of a metal construction as are the riser support plates and longitudinally extending guide rods, and the side members and spacer 8 may be of wood or metal construction and the various washers used in the construction could alternatively be of metallic construction or of plastic material such as nylon or the like.

I claim: i

1. A molding assembly for cement or concrete staircase construction, including a plurality of riser support plates each having a substantially upright edge adapted I to be secured to a riser mold board against which concrete is poured, the riser support plates being spaced along and pivotally carried by an elongate support member which is adapted to be positioned at the angle of inclination of the staircase, the elongate support member consisting of two spaced apart and parallel side members held in position by spacer members, the riser support plates being positioned partially between the side members, each of the riser support plates having an aperture positioned substantially centrally along its upper edge and major pivot pins passing through the apertures and into the side members with the riser support plates being pivotable on their respective major pivot pins, and elongate guide means extending longitudinallyof the elongate support member, the riser support plates being spaced along and pivotally secured to the elongate guide means, whereby longitudinal movement of the elongate guide means imparts uniformrotational movement to each of the riser support plates.

2. An assembly according to claim 1, wherein the plurality of riser support plates include a lower riser support plate positioned at one end of the elongate support member, the lower riser support plate having a bottom edge positioned substantially 90 to its upright edge, the remaining riser support plates having bottom edges forming an acute angle with their respective upright edges.

3. An assembly according to claim 1, wherein the upright edges are provided with angled flanges having holes provided therein and through which nails or bolts pass to secure the riser mold boards thereto.

4. An assembly according to claim 1, further including means to solidly secure the said support member against movement during pouring of concrete or cement.

5. An assembly according to claim 2, wherein the elongate guide means being pivotally secured to the riser support plates by corner pivot pins passing through corner apertures provided in an upper corner 8 of each risersupport plate remote from said upright edges.

6. An assembly according to claim 5, wherein the elongate guide means is a guide rod, the corner pivot pins passing through the corner apertures and the guide rod.

7. An assembly according to claim 6 wherein the major pivot pin passing through the centrally positioned aperture in the lower riser support plate is received in an aperture provided in the elongate support member and restrained against longitudinal movement,

' and the major pivot pins passing through the centrally positioned apertures in the remaining riser support plates being received in longitudinal elongate slots provided in the elongate support member and means to selectively move the remaining riser support plates longitudinally of the elongate support member, and means to selectively move the said remaining riser support plates longitudinally of the elongate guide means.

8. An assembly according to claim 7, wherein the corner pivot pins are secuted to sleeves encircling and carried bythe elongate guide rod, the sleeves being movable longitudinally of the guide rod and having set- 4 screws to maintain the sleeves in selected position along the guide rod.

9. An assembly according to claim 8, wherein the means to selectively move the remaining riser support plates longitudinally of the elongate support member consists of a lazy tong linkage, each alternate pivot of the lazy-tong linkage being pivotally secured to a major support pin.

10. An assembly according to claim 8, wherein the means to selectively move the remaining riser support plates longitudinally of the elongate support member consists of a threaded sleeve connected to each major pivot pin and a length of threaded adjustment rod extending between and threading into each adjacent threaded sleeve, the threading on each of the ends of the threaded adjustment rods being reversed whereby rotation of a threaded adjustment rod in one direction moves adjacent threaded sleeves and pivoted riser support plates closer together and rotation of a threaded adjustment rod in the other direction moves adjacent threaded sleeves and pivoted riser support plates farther apart.

l1. Anassembly according to claim 8, wherein the substantially upright edge on each riser support plate is provided with an adjustable riser board support plate pivotally secured thereto, the said adjustable riser board support plate having means to secure a riser mold board thereto, and means to secure the said adjustable riser board support plate at an angle to said upright edge. 

1. A molding assembly for cement or concrete staircase construction, including a plurality of riser support plates each having a substantially upright edge adapted to be secured to a riser mold board against which concrete is poured, the riser support plates being spaced along and pivotally carried by an elongate support member which is adapted to be positioned at the angle of inclination of the staircase, the elongate support member consisting of two spaced apart and parallel side members held in position by spacer members, the riser support plates being positioned partially between the side members, each of the riser support plates having an aperture positioned substantially centrally along its upper edge and major pivot pins passing through the apertures and into the side members with the riser support plates being pivotable on their respective major pivot pins, and elongate guide meanS extending longitudinally of the elongate support member, the riser support plates being spaced along and pivotally secured to the elongate guide means, whereby longitudinal movement of the elongate guide means imparts uniform rotational movement to each of the riser support plates.
 2. An assembly according to claim 1, wherein the plurality of riser support plates include a lower riser support plate positioned at one end of the elongate support member, the lower riser support plate having a bottom edge positioned substantially 90* to its upright edge, the remaining riser support plates having bottom edges forming an acute angle with their respective upright edges.
 3. An assembly according to claim 1, wherein the upright edges are provided with angled flanges having holes provided therein and through which nails or bolts pass to secure the riser mold boards thereto.
 4. An assembly according to claim 1, further including means to solidly secure the said support member against movement during pouring of concrete or cement.
 5. An assembly according to claim 2, wherein the elongate guide means being pivotally secured to the riser support plates by corner pivot pins passing through corner apertures provided in an upper corner of each riser support plate remote from said upright edges.
 6. An assembly according to claim 5, wherein the elongate guide means is a guide rod, the corner pivot pins passing through the corner apertures and the guide rod.
 7. An assembly according to claim 6 wherein the major pivot pin passing through the centrally positioned aperture in the lower riser support plate is received in an aperture provided in the elongate support member and restrained against longitudinal movement, and the major pivot pins passing through the centrally positioned apertures in the remaining riser support plates being received in longitudinal elongate slots provided in the elongate support member and means to selectively move the remaining riser support plates longitudinally of the elongate support member, and means to selectively move the said remaining riser support plates longitudinally of the elongate guide means.
 8. An assembly according to claim 7, wherein the corner pivot pins are secuted to sleeves encircling and carried by the elongate guide rod, the sleeves being movable longitudinally of the guide rod and having set-screws to maintain the sleeves in selected position along the guide rod.
 9. An assembly according to claim 8, wherein the means to selectively move the remaining riser support plates longitudinally of the elongate support member consists of a lazy-tong linkage, each alternate pivot of the lazy-tong linkage being pivotally secured to a major support pin.
 10. An assembly according to claim 8, wherein the means to selectively move the remaining riser support plates longitudinally of the elongate support member consists of a threaded sleeve connected to each major pivot pin and a length of threaded adjustment rod extending between and threading into each adjacent threaded sleeve, the threading on each of the ends of the threaded adjustment rods being reversed whereby rotation of a threaded adjustment rod in one direction moves adjacent threaded sleeves and pivoted riser support plates closer together and rotation of a threaded adjustment rod in the other direction moves adjacent threaded sleeves and pivoted riser support plates farther apart.
 11. An assembly according to claim 8, wherein the substantially upright edge on each riser support plate is provided with an adjustable riser board support plate pivotally secured thereto, the said adjustable riser board support plate having means to secure a riser mold board thereto, and means to secure the said adjustable riser board support plate at an angle to said upright edge. 